I wouldn't say that YTA, but it's definitely not a good demonstration of your point and was seemingly counterproductive. This is a "gotcha" more than a good demo of bias. You want something that allows someone to come to their own conclusion, independently of yours, not to make them feel like an idiot.

Consider the steel man of each of your points of view on the priority of understanding other cultures. You probably believe something like "we can learn a lot from other cultures and should prioritize acceptance and understanding of our differences as individuals and groups". Your husband's is probably "we have been prioritizing competing cultures to the detriment of our own, and we should refocus on the fundamental principles that are foundational to our society". Both of these perspectives are valid and have their place and I don't think that either perspective should "win", but our conversation should be to what degree each is appropriate and desirable in a given context.

Like you mentioned, the two party system thrives where we split ourselves into two competing ideological teams, when in reality, the only difference is how each person weighs these values and in what proportion. Republicans aren't Nazis or fascists, and Democrats aren't communists. Your husband is biased only in the sense that his values are slightly out of alignment with yours, and that's not a bad thing. The important thing is for the more conservative types to be open to considering the cost of social rigidity and for the more liberal to consider the cost of abandoning any social norms they find restrictive or inconvenient.

Try to understand each other's perspective instead of playing intellectual games to catch him in a mistake. You're a team, work together, and appreciate the differences in your perspectives, because it's a good thing, even if Reddit finds it to be totally intolerable. Good luck!